Compliant control for a cable-actuated anthropomorphic robot arm: An experimental validation of different solutions

This paper presents a research work on compliant control of an anthropomorphic robot arm used as a 'personal robot', for assistance to humans in different aspects of their everyday life. In personal applications of robotics, human-robot interaction represents a critical factor for a robot design and introduces strict requirements on its behavior and control, which has to ensure safety and effectiveness. In this work, the problem of controlling the Dexter anthropomorphic robot arm with variable compliance has been investigated, not only to ensure safety in the interaction with humans, but especially to increase the robot functionality in tasks of physical interaction, performed in co-operation with humans. Two different control schemes have been formulated and implemented on the peculiar structure of the robotic arm, so as to compare their performance through experimental trials. Both schemes aim at realising a self-controlled compliant behavior without using information from force/torque sensors. The experimental comparison outlines how the performance of the two control systems are inverted with respect to the theoretical considerations, based on the classical control theory, on their accuracy and effectiveness. The paper firstly describes the two implemented control systems; then, the performance of the two controllers in the experimental trials are shown and compared, and the functional compliance of the better one is graphically demonstrated.